Observations on the Migration of Bacillus Spores Outside a Contaminated Facility During a Decontamination Efficacy Study

Abstract

The fate and transport of Bacillus anthracis spores in indoor and outdoor environments is not well understood. The Bio-Response Operational Testing and Evaluation exercise evaluated decontamination technologies in a twostory building experimentally contaminated with Bacillus atrophaeus subspecies globigii spores. The Bio-Response Operational Testing and Evaluation project provided a means to evaluate the potential for the spores dispersed inside the building to migrate to the outside as well as to investigate a new method for processing soils contaminated with Bacillus spores. Duplicate sterile sand samples were placed within the tent covering the building, but outside the building itself, near entrances, exits, and high-traffic areas to assess migration and deposition of newly disseminated spores. The sand samples were utilized during three stages of the decontamination study: before spore dissemination, after spore dissemination, and after decontamination of the building. In addition, two sets of sand samples placed within the building provided positive controls. Results from two different building decontamination approaches were studied. Results were tabulated as presence or absence rather than as a quantitative figure. There was no significant association among positive samples and the location of the samples around the building. There was a significant association between the different stages of each decontamination study and the number of detectable samples. The results of this study demonstrate the potential for spores to migrate out of a contaminated building and the importance of considering migration when assessing the scope of a contamination incident